By way of introduction, a digitizer system for tracking an electronic pen enables hand written documents and drawings to be tracked and stored electronically. The writing movements produced by these devices are traced and recorded, and as a result the textual and graphical content can be digitized and stored in memory and/or persistent storage. Some digital writing systems include optical character recognition (OCR) software for converting recorded pen strokes to text data. The term ‘electronic pen’ refers to pen with ink or to an inkless stylus. Digital writing instruments or styluses, interchangeably referred to herein as “digital pens” regardless of whether or not they write in ink, can be used to capture pen strokes and digitize them. The electronic pen communicates with a base unit of the digitizer system using a communications method that typically includes at least one of infrared signals, ultrasound signals and other communications method. The base unit also communicates with an external device such as a personal digital assistant (PDA) to record the movements of the electronic pen or stylus.
Various sensors detect and digitize the location of the pen, such that the writings, drawings or scribbles of the pen are stored, for example, into a computer file. The location of the digitizer pen is tracked with a device tracking mechanism. Those devices typically employ a combination of transmitters, especially ultrasound and infrared transmitters, and receivers for processing signals. The position of the movable implement is then derived by triangulation. These systems typically may require additional hard-wired or electromagnetic link, such as an infrared link, between the movable implement and a base unit whose position is fixed in space, to provide timing information for time-of-flight ultrasound calculations.
It is noted that digital writing systems have been described in several patent documents, including U.S. Pat. Nos. 6,876,356, 5,198,623, JP. Pat. No. 11,085,378 and U.S. Pat. No. 6,104,388 (incorporated herein by reference).
It is thus noted that digital pens may include one or more of the following elements: (i) a sound transducer (for example, a sound transmitter and/or receiver, for example, including piezoelectric film), (ii) a ‘pen-up/pen-down’ sensor for sensing if the digital pen is in contact with a writing surface (or pressed to the writing surface), and (iii) an optical transmitter and/or optical receiver (for example, infrared transmitter and/or receiver).
A brief discussion of certain implementations of each of the aforementioned elements is provided below. Furthermore, it is noted that certain digital pens may also be used as mouse devices, and a brief discussion of certain issues related to using a digital pen also as a mouse device is also provided below.
Digital Pens that Include Sound Transmitters
FIG. 1 shows a distal portion of a digitizer pen, for example a digitizer pen disclosed in U.S. Pat. No. 6,876,356 of the present inventors, showing the digitizer pen designed as a cylindrical housing 10 having a central longitudinal axis 15, including a rigid writing implement 12 disposed along axis 15; and at its lower end, a narrower region 11 surrounded by a piezoelectric film 14 for transmitting sound signals Furthermore, the pen device includes an optical transmitter (or optical receiver) for providing synchronization information. Ultrasound transmitter is formed as a substantially cylindrical piezoelectric transmitter element attached to the lower end of housing 10. When piezoelectric transmitter element resonates, it produces an output sound wave which propagates perpendicularly to axis 15, as illustrated in FIG. 1.
Unfortunately, because of the propagation of the signals perpendicularly to the pen longitudinal axis, a significant attenuation of the detected signal is detected by the receivers. Interfering noise, created around the ultrasound transmitter, decreases the signal to noise ratio in the detected signal, decreasing accuracy and resolution. Therefore there is an ongoing need for electronic pen systems that facilitate more accurate determinations of pen position.
Digital Pens that Detected ‘Pen Up and/or Pen Down’ and/or Pressing of the Digital Pen to a Writing Surface
Moreover, in many applications, the pen or stylus (i.e. having a point) is used by the user to ‘write’ or perform strokes on a given surface. Thus, when the stylus or pen is “down” (i.e. contacting the surface), the location of the pen at any given moment may be tracked in order to perform pen strokes. When the pen is “up” (i.e. hovering over the surface) the location of the pen may be tracked in order to provide the “mouse mode,” or, alternatively, can be in “idle” status. Therefore an additional system is also required in order to determine when the user is writing and when the user is just moving the pen (i.e. to determine ‘pen-up’ or ‘pen down’). Various systems are used to identify when the movable element is in contact with the writing surface and to determine when the user is writing as well as the fineness or thickness of a line being drawn.
In certain devices, for example as disclosed in U.S. Pat. No. 6,104,388 to Katsuharu et al., contact and pressure detectors are usually incorporated in the digitizer pen as a self-contained element including electronic circuitry.
Thus, as shown in FIG. 2, a sensor 16 (life for detecting a longitudinal force on elongated rod 13) is provided separately from printed circuit board PCS 18 which hosts electronics for operating an ultrasound transducer and/or an optical transmitter or receiver useful for sending or receiving signals for determining pen location. Unfortunately, this configuration (i.e. where sensor 16 is provided separately from PCT 18) might, in some situations, increase the manufacturing cost of the pen and/or make the pen less effective or convenient to use.
Digital Pens that Include Optical Transmitters
Digitizer pens frequently include an infrared transmitter. The IR signal may provide synchronization information, and may also provide additional information—for example, writing color information. Conventionally, infrared light sources are implemented at the distal end of a digitizer pen for directing infrared radiation emitted thereby through the pen housing as illustrated in FIG. 3. Because of the cylindrical shape of the housing, the infrared interface must have 360 degrees angular communications range around the pen longitudinal axis, to transmit an accurate signal. Typically, a plurality of infrared light sources (17), such as light-emitting diode (LED), reside ‘externally’ on a surface of the pen housing 19 and are located at various locations around housing 19 to obtain a good uniformity of the light transmission over the 360 degrees angular communications range around the pen longitudinal axis. Unfortunately, the need for multiple LEDs makes the device more expensive to manufacture, and it would be desirable to have a digital pen that requires fewer LEDs and/or provides light transmission of multiple beams of light per LED.
A Brief Discussion Related to Using a Digital Pen as a Computer Mouse
Certain digital writing systems provide two modes of operations—“digital pen mode” for tracking pen strokes, and a “mouse mode” where translation of the digital pen serves to provide movement of a “mouse locator” within the host system. The term “mouse” refers hereinafter to any device that a computer user pushes across a surface, such as a mouse pad or desk surface, in order to point to a place on a display screen of a computing device and/or to select one or more actions to take from that position. Towards this end, digital pens associated with these systems typically include a button deployed to the housing of the digital pen for providing “mouse clicks” on the host device. There are a number of applications for these such multifunctional systems. According to one specific example, a user may read certain electronic material (for example, by surfing the internet) and write notes upon finding items of interest. These notes may be saved electronically and refereed to a later time. There is an ongoing need for improved electronic pen system where the electronic pen provides both ‘pen mode’ and ‘mouse mode.’ In particular, there is an ongoing need for improved mechanisms for switching between pen mode and mouse mode and there is an ongoing need for improved ‘writing’ or ‘linked’ electronic pen devices that provide both pen mode and mouse mode.